391191985 has 4 divisors (see below), whose sum is σ = 469430388. Its totient is φ = 312953584.

The previous prime is 391191967. The next prime is 391192001. The reversal of 391191985 is 589191193.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 589191193 = 617 ⋅954929.

It can be written as a sum of positive squares in 2 ways, for example, as 260112384 + 131079601 = 16128^2 + 11449^2 .

It is a cyclic number.

It is not a de Polignac number, because 391191985 - 2⁹ = 391191473 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39119194 + ... + 39119203.

It is an arithmetic number, because the mean of its divisors is an integer number (117357597).

Almost surely, 2^391191985 is an apocalyptic number.

It is an amenable number.

391191985 is a deficient number, since it is larger than the sum of its proper divisors (78238403).

391191985 is an equidigital number, since it uses as much as digits as its factorization.

391191985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78238402.

The product of its digits is 87480, while the sum is 46.

The square root of 391191985 is about 19778.5738869111. The cubic root of 391191985 is about 731.3579433999.

The spelling of 391191985 in words is "three hundred ninety-one million, one hundred ninety-one thousand, nine hundred eighty-five".